1. Field of the Invention
The instant invention relates to that field of devices consisting of articles of manufacture known as hand carts. Specifically, the instant invention is a foldable cart having a specialized wheel and wheel bearings for traversing colloidal and soft soil environments such as sand, snow and the like.
2. Background Information
The prior art known to applicant discloses that hand carts are well known. Prior art hand carts have been specifically configured for use in sandy and other soft soil environments. These carts (usually referred to as beach carts) have included features which allow them to serve as seats in addition to being useful for transporting the various accessories that are often carried along to the beach, such as towels, coolers and such. An example of such a cart is found in the U.S. Pat. No. 2,967,058 (1961) issued to W. H. Hoffmann, Jr. In Hoffmann, the combination beach barrow and chair is a beach cart having at its terminating end an essentially barrel shaped wheel, a pair of substantially straight frame rails extending from the wheel and meeting to form a handle, and a cloth or similar material sling located between the handle and the wheel. An essentially "U" shaped brace depends perpendicularly from the frame rails, and provides support when the device is used as a beach chair. Unfortunately, Hoffmann's device is difficult to use, in practice. Articles placed within the sling/seat tend to slide forward towards the wheel. This, in turn, places the bulk of the weight being carried behind the wheel, thereby shifting much of the weight to the handle (and therefore, to the user of the device.) Furthermore, the device is bulky and includes no means for folding or otherwise facilitating easy storage.
Other devices have attempted to overcome the problem of bulkiness by introducing foldability. A fine example of such a foldable beach cart may be found in U.S. Pat. No. 3,677,571 (1972) issued to Maturo, Jr. et al. Maturo's device included a pair of matched pivot points which permitted the device to be folded in two places, thereby reducing the device's bulkiness when stored.
Maturo's device, however, included a defect similar to Hoffimann's. In Maturo, the device's "basket" is located forward of the wheel or roller. Therefore, when in use, the device had a tendency to tilt forward, thereby interfering with the device's travel across lose soils such as sand. A user of the device who attempted to overcome this forward tilting tendency would likely lean the device further back, toward the user. So doing had the distinct disadvantage of shifting a greater amount of the payload weight into the hands of the user. In short, Maturo, like Hoffinan, fails to recognize the necessity for a well placed, and easily maintainable, center of gravity.
The beach carts found in the prior art have also sought to provide wheels which are suitable for travel over the loose, particulate surface conditions found at a beach. For example, in Maturo, the wheels are comprised of a single roller assembly having upon it a series of longitudinal and transverse wires which foraminously enclose the wheel. These wires provide far more "bite" into the sandy soil than would a smooth cylindrical or tubular wheel. A slightly different approach to solving the problem of wheel traction on loose soils is found in U.S. Pat. No. 4,362,308 (1982), issued to Hicks et al. In Hicks, the wheel is a single cylinder comprising a pair of oppositely aligned end caps having an axially located center hole therethrough, a ribbed roller section having a plurality of longitudinally extending ribs positioned radially about a longitudinal axis, and an axle which is coaxial with the ribbed roller section and engages the end caps through the center holes.
Applicant has discovered that while incorporation of wire mesh or longitudinal ribs onto the beach cart wheel provides a better bite into loose or granular soils than do smooth wheels, the loose soil still had a tendency to "pile up" in front of the wheel as it moved forward. Such accumulation of materials in front of the wheel forces the user to invest greater effort into moving the beach cart forward in order to pass over the accumulated soils.
The prior art generally known to Applicant also indicates that wheels for use in loose or granular environments such as sand are especially vulnerable to damage caused by the unwanted intrusion of particulate matter into the wheels, wheel hubs, and various friction reduction means such as race bearings. Such intrusion has the unwanted effect of creating additional friction in the wheel which is experienced by the user of the beach cart as "resistance" to pushing or pulling. A further undesirable effect of particulate matter intrusion is the uncontrollable degradation of the wheel component parts, and the of times unanticipated failure of the wheel assembly as a result.